This disclosure relates in general to the field of centrifugal separators, and more particularly to a system and method for vibration in a centrifuge.
The demand for efficient removal of contaminants from water supplies has increased. Because of their relatively small size, many light density contaminants (e.g., microorganisms) may often not be removed by conventional processing methods including fluid separation.
Fluid separation may include any process that captures and removes materials from a liquid stream, typically resulting in a clarified liquid having reduced contaminants and a denser stream containing removed contaminants. Further treating the denser stream in a thickening process may remove additional liquid to leave a thick, pump-able slurry mixture containing nine percent to approximately twelve percent solids by weight. Under certain conditions, a de-watering process may remove more water from the slurry mixture. The de-watering process may create a stackable but still moist mixture of approximately twelve to thirty percent solids by weight. In an extreme de-watering process, the resulting mixture may have up to forty percent solids by weight. In treating a clarified liquid, an associated clarifying process may remove suspended solid particles leaving a substantially further clarified fluid.
One example of a fluid separation technique may include a membrane filtration process. Typically, a membrane filtration process removes particles from a liquid by retaining the particles in a filter of a specific size suited for a particular application. Some examples of membrane filtration processes include microfiltration, ultrafiltration, and nanofiltration. For insoluble particles, microfiltration can be used to retain and remove these particles from a liquid. Ultrafiltration may define a purification process that serves as a primary purification filter to isolate a desired solid product of a specific size. Nanofiltration may remove contaminants as small as microscopic bacterial cyst in a final purification process.
Another example of a fluid separation technique may include centrifugal separation. A centrifuge may use centrifugal force to separate contaminants from a fluid medium by producing a denser stream containing removed contaminates and a clarified fluid stream with less contaminates. Typically, the centrifugal force is several times greater than gravity, which causes more dense contaminants to separate from the fluid medium. During separation, the fluid medium is often placed within a chamber that rotates along a symmetrical axis creating the centrifugal force in a radial direction away from the symmetrical axis. More dense contaminants suspended in the fluid medium are forced against an outer wall of the rotating chamber and may pass through openings in the chamber to an outer catchment basin. The resulting clarified fluid, which is less dense, remains near the axis of rotation and may typically be removed from the chamber via a clarified fluid outlet.
The centrifugal force that drives more dense contaminants to contact the outer walls may create a frictional force between the outer walls and the contaminants. Such frictional forces vary depending on the shape of the outer walls and, in some instances, may impede movement of contaminants towards the openings in the outer wall. As a result, some of the contaminants may remain trapped against the outer walls of the chamber without being removed from the fluid medium. Problems may also occur if the shape of the outer walls allows the fluid medium to pass out of the associated openings before contaminants are separated from the fluid.
In accordance with teachings of the present invention, disadvantages and problems associated with a centrifuge have been substantially reduced or eliminated. In one embodiment, a centrifuge for separating more dense material from a fluid medium includes a fluid separation wall placed within a non-rotating sleeve. The fluid separation wall may rotate around a generally symmetrical axis of rotation and may include an inner surface and an outer surface with at least one receptacle formed on the inner surface of the fluid separation wall. The receptacle may aid in separation of more dense material from the fluid medium by forming a void space between the inner and outer surface. An excitation apparatus may be associated with the receptacle to create vibration within the receptacle. A flow path may extend through the wall from the void area to an outer surface of the wall to transport more dense material to a containment zone.
In another embodiment of the present invention, a fluid separation wall for separating more dense material from a fluid medium in a centrifuge may include an outer shell operable to receive a plurality of replaceable receptacles. The plurality of replaceable receptacles may aid in separation of more dense material from a fluid medium. Each replaceable receptacle may have an inner surface, a middle section, and an outer surface. A respective geometry may be formed on the inner surface for each receptacle. A receptacle shape may be formed in the middle section of the receptacle such that the receptacle shape interacts with the fluid medium. The inner surface of one or more replaceable receptacles may be in communication with the fluid medium. The outer surface of one or more replaceable receptacles may couple to the outer shell. A vibratory device may be associated with the replaceable receptacle.
In a further embodiment of the present invention, a method of removing more dense material from a fluid medium may include forming a centrifuge core with at least one receptacle having an opening and a flow path extending therethrough. The method may include forming a centrifuge with the centrifuge core disposed within an outer non-rotating collecting sleeve. The method may further include rotating the centrifuge core around an axis of rotation to create centrifugal forces to separate more dense material from a fluid medium by directing more dense material through one or more openings into a void area formed by the receptacle and through a flow path to a collection zone between the centrifuge core and a non-rotating sleeve. The method may include creating an excitation force within the centrifuge such that the excitation force imparts vibration to more dense material.
One technical advantage of the present invention may include reducing friction effect of a receptacle wall with respect to movement of more dense material along the wall. Vibration in the receptacle may create a xe2x80x9cslipperyxe2x80x9d wall effect thus reducing effective frictional forces imparted on more dense material against the walls. This xe2x80x9cslipperyxe2x80x9d wall effect may cause more dense material to proceed along the wall to an associated opening for separation from a fluid medium.
Another technical advantage of the present invention includes preventing or reducing compacting of more dense material in a receptacle during increased de-watering. Vibration may cause more dense material to collect in the receptacle and move through an associated opening. A build up of such more dense material may clog the opening further compacting more dense material, which removes more clarified fluid. Vibrations may then cause the particle to breakup at a desired operating condition thus removing the de-watered more dense material from the receptacle.
A further technical advantage of the present invention may include varying the velocity of separation of more dense material in a fluid medium. Steep or shallow walls on an interior of a receptacle wall may create frictional forces as more dense material moves towards an associated opening. The frictional forces may vary depending upon the angle or slope of the receptacle walls. By increasing the angle or slope, such as adding a steep wall, more dense material may move more rapidly toward the associated opening. This may decrease desired separation caused by centrifugal force since less dense fluid may be carried out an associated opening along with more dense material. Providing a shallow sloped wall one or more interior surfaces of a receptacle allows frictional forces to slow the movement of more dense material, which permits additional removal of liquids such as water from more dense material as it moves more slowly along the walls of the receptacle towards the associated opening. Vibrational forces may be incorporated with these sloped walls to further aid in separation of more dense material from the fluid medium.
All, some or none of these technical advantages may be present in various embodiments of the present invention. Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.